Effect of equal-channel angular extrusion on mechanical and wear properties of eutectic Al-12Si alloy

Mechanical and wear properties of severely deformed Al-12Si alloy by equal-channel angular extrusion/pressing (ECAE/P) were investigated. Multi-pass ECAE processing of the as-cast alloy substantially increased both its strength and ductility. The increase in the tensile and yield strength values after six ECAE passes were about 48% and 87%, respectively. The sample after six ECAE passes exhibited 10% elongation before rupture, which was about five times higher than that of the as-cast one. The improvement in both strength and ductility was mainly attributed to the changes of the shape, size and distribution of the eutectic silicon particles along with the breakage and refined of the large alpha-Al grains during multi-pass ECAE processing. However, the wear test results surprisingly showed that the ECAE process decreased the wear resistance of the alloy, although there was improvement in strength and ductility values. This was mainly attributed to the tribochemical reaction leading to oxidative wear with the abrasive effect in Al-Si alloys during sliding. The oxide layer played a dominant role in determining the wear resistance of the sample in both as-cast and ECAE-processed states, and it masked the effect of strengthening of alloy structure on the wear resistance. (C) 2009 Elsevier Ltd. All rights reserved.